Multiple switchboard for telephone-exchanges.



EATEETED MAY 29, 1906.

M. E. KELLUEG.

MULTIPLE SWIEGEEUAED EOE TELEPHONE EXCHANGES.

APPLICATION FILED NOV. 30, 1891.

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, tions of two switchboards to nnrrnn sirarns PATENT OFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SVVITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

Speccaton of Letters Patent.

ratented. May 291906.

Application filed November 30,1891. Serial No. 413,605.

To a/ZZ whom t may concern:

Be it known that I, Miro G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, temporarily residing at Geneva, in the Republic of Switzerland, have invented certain new and useful Improvements in Multiple Switchboards for TelephoneEXchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My inventionrelatcs especially to a metallic circuit system or to a system in which part of the lines are metallic-circuit lines, but is not in all respects limited to such a system; and it consists in a system for calling, testing, switching, and clearing out, which I shall describe and claim in detail.

In the accompanying drawings, illustrating my invention, Figure l is a diagram with secwillich the same lines are connected, with two lines and their central-ollice apparatus connected with the same. FiO. 2 shows an operators cord system adapted to be used at any board. Fig. 3 shows an operators test system adapted to be used at any board. Fig. 4 shows a subscribers station apparatusfor eachline. Fig. 5 shows a polarized annunciator which may be used for each line. Fig. 6 is an end view of the generator-shaft at the subscribers station with two contacts, one bearing on each side of the shaft` In Fig. l, A A are sectional views of sections of two switchboards. Each board has a switch for each line. Each switch has two contact-pieces insulated Jfrom each other (eX- cept through the circuit connections) and a switch-hole adapted to receive the switchplugs at its board. The contactpieces of the switches are so placed. and arranged that when a loop-switch plug (shown in Fig. 2 and marked D D) is inserted into the switch-hole the fronts of which are the switch-holes.

Other forms of switches may be used which have two contact-pieces insulated from each other and adapted to receive loop-switch plugs and Jform connection between their contact-pieces and the contact-pieces of the plug.

w w are line-annunciators, and are retardation-coils, one annunciator and one retardation-coil for each line. On account of the calling system which I shall describe it is preferable that the annunciators be polarized annunciators. One side or branch of each line is connected to one of the contact-pieces of each of the switches of the line-say pieces g g-#and the other contact-pieces-sayyl j are connected with the other side or branch of the line. One side or branch of each line-say the side which is connected to the contact-pieces g gis permanently grounded through the annunciator and retardation-coil of the line. rIhe connections shown in Fig. l are substantially as described above.

Inl Fig. 2, D D are a pair of loop-switch plugs, each plug being adapted to be inserted into each switch at its board and when inserted to form connection between its contact-pieces and the contact-pieces Vof the switch. The two contact-pieces of one plug are connected with the two contact-pieces of the other plug, respectively, by two flexible switch conductors. tis the operators telephone; R, a calling-generator g Y, a looping-in switch; o, a clearing-out annunciator, B, a test-battery in a loop with the telephone, and B a testbattery in a loop with the clearing-out annunciator. Each pair of plugs has a switch Y, a clearing-out annunciator v, and a testbattery B. One calling-generator will answer for the exchange. The connections are substantially as shown. By means of the looping-in switch Y the operator may at will bridge the circuit of the two iiexible conductors with either the loop containing her telephone and its test-battery or the loop containing the clearing-out annunciator and its test-battery or with the calling-generator- Only one pair of-plugs with their special apparatus is shown. Other pairs may be added to the operators cord system in a way which will be apparent to those skilled inthe art.

The clearing-out annunciators should pref- IOO ' at her board. f

In the subscribers-station apparatus,

, (shown i-n Fig. 4) 1 is the telephone-switch;

- lation, as shown in Fig. 6.

2, the calling-generator;,3, the signal-receiving bell; 4, the subscribers telephone; 5, a station-battery, and 6 a clearing-out key. These parts may be of usual kinds. The calling-generator is, however, modified as iollows: The insulated contact-piece on the shaft of the armature, to which is connected one end 'of the armature-wire and which conducts the generated current to the line through the stationary spring-contact (or contacts) provided for it, is a half-circle, the remaining part of the circle being an insu- I provide two stationary spring contact-pieces, as shown, (marked s 8,) bearing on the diametrically opposite parts of the circle ofthe shaft of which said insulated contact-piece is a part. The key 6 is provided with two pairs of contactpoints, as shown, one pair being normally closed and the other pair normally open, and when the key-lever is depressed the pair normally closed is opened and the normally open pair is closed. The connections of the key to the contactesprings of the generator and to the line-circuit is as follows and as shown: The spring-lever which forms one of the contact-points of each pair is connected to one side'or branch oi the line. The two other contacts of the key are connected to the two contact-springs of the generator, respectively. rlhe frame of the generator is connected with that contact-point of the telephone-switch which is in connection with the switch-lever when the telephone is on the switchv and the signal-receiving bell is in cir-` cuit with the generator. The lever of the switch is connected with the other side or branch of the line. The other contact-point of the switch (that against which the lever comes into contact when the telephone is taken from the switch) is connected to the rstementi'oned side of the line through the telephone and stationbattery. As is usual with this style of generator, (which is well known,) one terminal of the armature-coil is connected to the generator-frame and to the arm through which the generator is grounded when operated. As seen in Fig. 6, the generator is therefore normally shunted, but

caract when operated the shunt is opened and the armature grounded. It is evident from the drawings and the above description that when the telephone is on the switch the generator and bell are in circuit with the line and when the telephone is off the switch the telephone and battery are in circuit with the line.

It is well known that when the usual calling magneto-generator is operated acurrent oi one polarity is generated during half the revolution of the armature and a current of the other polarity is generated during the rest of the revolution. The contact-springs of the generator are so placed that one of them conducts the current of one polarity and the other the current of the other polarity. It will be apparent from the description of the generator and circuit connections which has been given that when the generator is operated with the subscribers telephone on its switch and the key is not depressed a current of one polarity will be generated in the line and when the key is depressed a current of the other` polarity is generated. The subscriber can therefore atwill send a current of either polarity.

The automatic device of the generator has a pair of contacts by which the line-circuit is automatically grounded While the generator is being operated. The apparatus should be so connected into the line-circuit that the generator is between this ground connection and the permanent ground connection of the line at the central oflnice.

The polarized annunciators should preferably be so connected into their respective circuits as to be operated by the current from the subscribers generator when it is operated and the key is not depressed. The polarized annunciator shown in Fig. 5 is substantially a modiiication of the non-polarized annunciator most generally used for telephone-exchanges and shown and described in detail in the patent of James C. Warner, No. 266,405, and dated October 24, 1882. The modification consists, essentially,` in the employment of a permanent magnet (marked N S) attached at one end to the iron plate which forms the pole-piece of the electromagnet of the annunciator and which therefore charges thel cores of the .electromagnet with one polarity of magnetism. The permarient magnet. is bent so that its other end is in close juxtaposition to the armature of the annunciator and charges the armature by induction. It is well known that when a current is sent through a, polarized annunciator of the polarity not to operate it there 'is no attraction whatever between the electromagnet and the armature of the annunciator, and therefore there is no tendency to release the annunciator-drop, so that it may fall and indicate a call. On the other hand, when such a current is passing through the annunciator there is a repulsion between the roc IIO

electromagnet and its armature, which, in fact, then positively holds down the catch of the annunciator and positively locks or prevents the release of the drop.

The clearing-out annunciators may be nonpolarized annunciators.

The operation of the system is as follows: When a subscriber wishes a connection, he operates his generator without pressing down his key-lever. A calling-current passes from the ground connection he thereby establishes and one branch of his line and the line-annunciator to the ground at the central ofiice v and operates the annunciator. The operator then places one of her switch-plugs in the switch of the line and the levers of the switch Y of the plug being in the position where the telephone bridges across the two contactpieces of the plug. She finds out by conversation what line is wanted. She then tests the line wanted, as will hereinafter be indicated, and if it tests free or unswitched she places the other plug of the pair in its switch. She then moves the switch Y so thatthe calling-generator is in a bridge connection across the two sides of the circuit established between the two lines and a callingcurrent will go in split current through the circuit of both lines and ring the bell of the subscriber wanted and also that of the calling subscriber if he has replaced his telephone on its switch. The operator then moves the switch Y so that the clearing-out annunciator, with its battery, is inthe bridge connection across the two sides of the circuit. The subscribers are then conneet-ed together for conversation and their circuit is grounded through the annunciators and retardation-coils of both lines. This, however, will'not interfere with telephone conversation which may be sent over the circuit. Tt is preferableA that the plugs be placed in the switches in such a direction that the annunciators and retardation-coils of both lines are connected to ground on the same side of the metallic circuit established between the lines. To send a clearing-out signal, either subscriber presses on his clearingout key and at the same time operates his calling-generator. A clearing-out current is therefore sent through his metallic circuit, and the clearing-out annunciator which bridges the circuit and the annunciator will be operated, indicating a clearing-out signal. i/Vhen the clearing-out signal is given, current will also go to ground through the annunciators of the lines. It will, however, not be of the polarity to operate the annunciators. When the subscriber sends the clearing-out signalas above described, and part of the current goes through the line-annunciators of the two lines, there is, on account of the polarity of the current and the construction of the annunciators, no attraction whatever between the line-annunciator magnets and their armatures, and consequent-ly there is no tendency or force whatever exerted to release the drop. There is, on the other hand, a repulsion between the two which acts at 'that time to postively lock and prevent the release of the drop. The drop is therefore positively prevented from being operated when the clearing-out current is sent and is, in fact, locked, so as to be prevented from falling. In other systems of exchange operation in which the line-annunciators of two connected lines are in circuit with the calling-generator operated to send a clearing-out signal there is an attraction between the line-annunciator magnets and their armatures, and consequently there is a tendency to release the drop, which is only prevented from being operated or released from the fact that the current is not strong enough to furnish sufficient attraction to move the armature and release the drop. In such a system the line-drops are prevented from being operated only by a margin of ady justment current or force, which may at times be diiiicult 'to obtain and be more or less unreliable, while in my system the lineannunciators are positively prevented from being operated by and the drops are, in fact, electrically locked to the current sent through the annunciators in sending the clearing-out signal, however strong the current may be, and the drops do not depend on not being operated when the clearingout current is sent by any mere margin of adjustment current or force. This result is obtained by the construction of the line-annunciators. So far as I am aware, this system of clearingout signals is generically new with me, and I do not limit myself to the specific means of positively preventing the operation of the line-annunciator drop when a current is sent from a subscribers station to operate the clearing-out annunciator, since, obviously, other ways may be devised of accomplishing such a result by theuse of devices operating in well-known ways.

The test system is as follows: /Vhen an operator tests a line, she places her test-plug on the contact-piece of the switch of the line. If then the line is switched for use and the circuit is bridged by either a telephone and its battery or the clearing-out annunciator and its battery or the calling-generator, a circuit is established which contains the testreceiving instrument and a source of electricity,l and the instrument will sound or respond. This circuit is from the ground to one side of the line, thence through the bridge connection which contains the source of electricity to the other side of theline, and to ground through its ground connection. If the line is not switched for use, but the subscriber has taken down his telephone for use, when the line is tested there is a complete circuit established from the ground through the test-receiving instrument .to the line and through the circuit of the line by way of the IOO IIO

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subscribers station and the battery which is then in the circuit at the subscriber s station back to ground at the central office through the line-annunciator, and the instrument will respond or sound. The test-receiving instrument will therefore sound whether the line is switched, for use or the subscribers telephone is switched for use. When neither is switched for use, the instrument will not sound. The test therefore indicates whether 0r not either the` line is switched or the sub- Ascribers telephone is switched for use.

The clearing-out annunciators, as heretofore stated, are preferably of comparatively high resistance and considerable retardation to telephone-currents, They therefore operate as retarding-coils to minimize the effect of the bridge or cross connection through the test-battery between the two sides or branches of the metallic circuit established for conversation between two subscribers.

The system might be modified by leaving the subscribers batteries out of the circuits, and the tests would indicate whether or not the lines were switched for use. It might also be modified by leaving the test-battery out of the bridge connections at the central office, and the tests would then indicate whether or not the subscribers telephones were switched for use.

Instead of the annunciator w and retardation-coil x for each line an annunciator may be employed which has high resistance and high retardation to telephone-currents.

I claim as my invention- 1. In a telephone-exchange system, metallic-circuit lines and polarized annunciators, one for each line through which one side or branch of the line is permanently grounded, in combination with switching apparatus to switch any two of said lines into a metallic circuit for conversation which does not include their annunciators, clearing-out annunciators, one in a bridge connection across each metallic circuit thus established, and calling apparatus at each subscribers station with commutator and switch parts to send at will a current of one polarity in a grounded circuit through the line-annunciator or when the line is switched a current of the other polarity in the metallic circuit through the clearing-out annunciator, substantially as set forth.

2. In a telephone-exchange system, a mesaijsof? scribers station to atwill send a current of either polarity into the line, and switch-contacts automatically operated by the generator to ground the line while the generator is being operated, substantially as set forth.

4. In a telephone-exchange system, a pair of loop-switch plugs, the two contact-pieces of one of which are respectively connected to the two contact-pieces of the other by two fieXible switch-conductors, in combination with an operators telephone and a test-battery in a temporary bridge connection across said conductors, substantially as set forth.

5. I n a telephone-exchange system, a pair of loop-switch plugs the two contact-pieces of one of which are respectively connected with the two contact-pieces of the other by two fieXible switch-conductors, in combination with a loop containing an operators telephone and a test-battery, another loop containing a clearing-out annunciator and a testbattery, and a looping-in switch with contacts and connections to at will connect either of said loops in a bridge connection across said conductors, substantially as set forth.

6. In a telephone-exchange system, tWo telephone-lines connected together in metallic circuit for conversation, in combination with an operators telephone and test-battery in a temporary bridge connection across said circuit, substantially as set forth.

7. In a telephone-exchange system, two telephone-lines connected together in metallic circuit for conversation, in combination with a loop containing an operators telephone and a test-battery, another loop containing a clearing-out annunciator and a testbattery, and a looping-in switch with contacts and connections to at will connect either of said loops in a bridge connection across said circuit, substantially as set forth.

8. In a telephone-exchange system, multiple switchboards, metallic-circuit lines connected to the boards, and two of said lines connected together in metallic circuit with one side of the circuit grounded, in combination with a loop containing a clearing-out annunciator and test-battery, another loop containing an operators telephone and testbattery, a looping-in switch with contacts and connections to at will connect either of said loops in a bridge connection across said ITO IIS

circuit, and test-receiving instruments, one

at each board, each grounded on one side and connected on the other side to a plug or device adapted to be brought, for testing one of said lines, into connection with the other side of said circuit, substantially as set forth.

9. In a telephone-exchange,. multiple switchboards, metallic-circuit lines connected to the boards, and two of said lines connected together in metallic circuit with one side of the circuit grounded through a retarding-coil, in combination with a loop containing an operators telephone and test-battery,

another loop containing .a clearing-out annunciator and test-battery, a looping-.in switch with contacts and connections to at will connect either of said loops in a bridge connection across said circuit, and test-receiving instruments, one at each board, each grounded on one. side .and connected on the other side to a plug or device adapted to be brought, for testing one of said lines, into connection with the other side of said circuit, substantially as set forth.

10. In a telephone exchange, multiple switchboards, metallic-circuit lines connected to the boards, and two of said lines connected together in metallic circuit with one side of the circuit grounded through the annunciator of one of said lines, in combination with a loop containing an operators telephone and testbattery, another loop containing a clearing-out annunciator and test-battery, a looping-in switch with contacts and connections to at will connect either of said loops in a bridge connection across said-circuit, and test-receiving instruments, one at each board, each grounded on one side and connected on the other side to a plug or device adapted to be brought for testing said lines into connection with the other side of said circuit, substantially as set forth.

11. In a telephone-exchange system, apair of loop-switch plugs the two contact-pieces of one of which are respectively connected with the two contact-pieces of the other by two flexible switch-conductors, in combination with a loop containing an operators telephone and a test-battery, another loop containing a clearing-out annunciator and a testbattery, another loop containing a callinggenerator, and a looping-in switch with contact and connections to at will connect either of said loops in a bridge connection across said conductors, substantially as set forth.

12. In a telephone-exchange system, two telephone-lines connected together in metallic circuit for conversation, in combination with a loop containing an operators telephone and a test-battery, another loop containing a clearing-out annunciator and a test-battery, another loop containing a calling-generator, and a looping-in switch with contacts and connections to at will connect either of said loops in a bridge connection across such circuit, substantially as set forth.

13. In a telephone-exchange system, mul# tiple switchboards, metallic-circuit lines connected to the boards, and two of said lines connected together in metallic circuit with one side of the circuit grounded, in combination with a loop containing an operators telephone and test-battery, another loop containing a clearing-out annunciator and testbattery, another loop containing a callinggenerator, a looping-in switch with contacts and connections to at will connect either of said loops .in a bridge connection across said circuit, and test-receiving instruments, one

at each board, each grounded onone side and connected on the other side to a plug or del vice adaptedto be brought, g-for testing one of said lines, `into connection with the other side of said circuit, substantially as set forth.

14. In a telephone-exchange system, multiple switchboards, a metallic-circuit telephone-line grounded on one side atthe central oiiice and temporarily switched in a metallic circuit for conversation, in combination with a test-battery in a bridge connection across the two sides of the line, a battery at the subscribers station in the circuit of the line while the subscribers telephone is switched for use and only then, and test-receiving instruments, one at each board, grounded on one side and connected on its other side to a plug or device adapted to be brought for testing into connection with the line on.its other side, substantially as set forth.

15. In a telephone-exchange system, multiple switchboards, a metallic-circuit telephone-line grounded on one side at the central ofiice and temporarily switched in a metallic circuit for conversation, in combination wi th a testebattery and a retarding-coil in a bridge connection across the two sides of the line, a battery at the subscribers station in the circuit of the line while the subscribers telephone is switched for use and only then, and test-receiving instruments, one at each board, grounded on one side and connected on its other' side to a plug or device adapted to be brought for testing into connection with the line on its other side, substantially as set forth.

16. In a telephone-exchange system, multiple switchboards, a metallic-circuit telephone-line grounded on one side at the central oiiice through a retarding-coil and temporarily switched in a metallic circuit for conversation, in combination with a test-battery in a bridge connection across the two sides of the line, a battery at the subscribers station in the circuit of the line while the subscribers telephone is switched for use and only then, and test-receiving instruments, one at each board, groundedv on one side and connected on its other side to a plug or device adapted to be brought for testing into connection with the line on its other side, substantially as set forth.

17. In a telephone-exchange system, two telephone-lines temporarily connected together into a complete circuit for conversation, in combination with a calling-generator at one of the subscribers stations of the two lines, operated to send a current of one polarity only to give the primary or calling signals of the line and to send a current of the other polarity only to give a clearing-out signal when the lines are thus connected, and a special clearing-out annunciator and the line- IOO IIO

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annunoators of the tWo lines which are then nalI but to respond to the current sent for the Io or when the clearing-out si nal is sent in primary oallingesignal.

. closed circuit with Said oa 1ing-generator, In testimony whereof I have hereunto subsaid clearing-out annunoator responding or scribed my name. indoatn@o and said line-annunoators being in circuitD with their generators when oper- MIL() G KELLOGG ated and polarized and connected in polarity Witnesses:

so as not to respond to the current thus sent l ANNA P. KELLOGG7 from the generator for the clearing-out sig- LEROY D. KELLOGG. 

